reduce grammar duplication

Author: vuvova

sql/sql_yacc.yy

@@ -6633,19 +6633,7 @@ serial_attribute:
             lex->last_field->flags|= PRI_KEY_FLAG | NOT_NULL_FLAG;
             lex->alter_info.flags|= Alter_info::ALTER_ADD_INDEX;
           }
-        | UNIQUE_SYM
-          {
-            LEX *lex=Lex;
-            lex->last_field->flags|= UNIQUE_KEY_FLAG;
-            lex->alter_info.flags|= Alter_info::ALTER_ADD_INDEX;
-          }
-        | UNIQUE_SYM KEY_SYM
-          {
-            LEX *lex=Lex;
-            lex->last_field->flags|= UNIQUE_KEY_FLAG;
-            lex->alter_info.flags|= Alter_info::ALTER_ADD_INDEX; 
-          }
-        | COMMENT_SYM TEXT_STRING_sys { Lex->last_field->comment= $2; }
+        | vcol_attribute
         | IDENT_sys equal TEXT_STRING_sys
           {
             if ($3.length > ENGINE_OPTION_MAX_LENGTH)